What would be the best method to fix the rust here under my window seals?

I dont think there is enough space to weld in a new piece of steel.

Lead wiping would not work as I cannot get to the rear of the panel to clean it ..

Should I take the bog option??

what about wire buffing it pretty hard then rust converting the rest and then bog ( evil word )

Cut it out and weld a patch in.
Rob.....

Either have it welded, or if you're using any sort of bog any time, get marine epoxy based bog, completely unaffected by water which normal car bog is NOT (slightly porous, relies on paint finish for protection). You can make it yourself ot buy ready made from marine paint/glue suppliers. If making up your own, get micro balloons (micro fine glass beads, better than talc which is used in car bog) and tell the supplier what you want the resin for. they will give you a relatively thick resin with a reasonable go off time. Beautiful to work with, about the consistency of ice cream